The generation of dust in the handling of certain finely divided solid materials or in the handling of "fines" present among larger particles, is a known problem. One area where this problem has been observed is in the handling of fertilizer materials. Dust is frequently generated in the handling of dry fertilizers. Dust can be a nuisance and may pose safety and health hazards. Dust problems are particularly severe in bulk fertilizer production and in distribution facilities that handle large quantities of dry fertilizers. When loading or unloading large quantities of such materials, the dust generated results in poor working conditions. A portion of the solid is lost and the surrounding may be contaminated with the settling dust. The United States Government has issued regulations to control dust exposure in the work place and to limit the amount of dust released into the environment.
The problem of preventing dust formation has been handled by spraying a liquid onto the solid material. Examples of this may be found in U.S. Pat. No. 3,393,973, to Almy, (tall oil sprayed on potash); U.S. Pat. No. 4,717,555 to Newman, et al. (naphthalene sulfonates and water on ammonium salts preventing caking and dust formation); and U.S. Pat. No. 5,041,153 to Detroit (lignosulfonate treated inorganic chemicals resist caking and dust).
Waxes and oils have also been applied to fertilizer powders to prevent dust formation. Such is described in European Patent Publication 0 255 665.
Russian Inventor's Certificate 2019535 C1 describes the use of glycerol residuum (bottoms formed in the distillation of crude glycerol) applied to potassium chloride as an anti-dusting agent.
Ammonium sulfate has been granulated to improve particle size distribution. U.S. Pat. No. 4,277,253 to Walter et al. describes the granulation of ammonium sulfate and other fertilizer ingredients.
Lobeco Products Inc. offers an anti-caking and anti-dusting product under the name Galory.TM. ATH 632. Galoryl ATH 632 is a solid at ambient temperature and must be heated (to about 80.degree. C.) to the liquid state before application. This adds to the handling difficulty and contributes to the safety precautions that must be in place to prevent burns from spillage of heated liquids.
In addition to the handling difficulties, such sprays are expensive and add significantly to the production cost of free-flowing, dust-free granules. Therefore, there remains a need for safely and economically producing granules that remain free-flowing and dust-free even after storage and shipping.
Water is an effective anti-dusting agent. Water, however, usually causes the material, e.g., ammonium sulfate, to cake. An effective anti-dusting agent will not contribute to the caking problems observed with many of the solid materials to which the present invention relates.